Washington (CNN)Despite plenty of disagreement during President Barack Obama's town hall on guns, there was one point on which he and his critics agreed: There isn't enough enforcement of the laws already on the books.

Why that is, though, is contested. And whether the barriers can be addressed without rewriting those laws will have a big effect on whether the executive measures announced by Obama this week will have much impact.

The President expressed frustration at the "Guns in America" forum hosted by CNN on Thursday night at his opponents telling him to enforce existing laws, saying those same opponents are trying to undermine them.

"One of the most frustrating things that I hear is when people say -- who are opposed to any further laws -- 'Why don't you just enforce the laws that are on the books?'" Obama said. "And those very same members of Congress then cut (Bureau of Alcohol, Tobacco, Firearms and Explosives) budgets to make it impossible to enforce the law."

Obama said some of his new proposals are designed to get at the issue of resources and the difficulties using existing law, including adding ATF agents and clarifying statutes to make them more usable.

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At the same time Obama was speaking, the National Rifle Association, a gun-rights lobby that skipped the town hall, was tweeting its dissatisfaction.

Pro-gun-control experts and some former law enforcement officials say that a lack of resources combined with vague and toothless laws make federal gun prosecutions difficult. And they accuse gun lobbies of intentionally watering down legislation and hamstringing agencies so the laws are useless, a point lobbyists contacted by CNN declined to address.

The Department of Justice said the President is calling for more resources and that the agency uses a "smart on crime" policy.

"The Department focuses its investigative and prosecutive resources on enforcement that will have the greatest impact on violent crime in our communities," spokesman Patrick Rodenbush said in a statement. "The Department's violence reduction activities seek to prevent firearms from getting into the hands of prohibited individuals, not just to prosecute individuals after they have committed a crime."

Gun-rights groups dispute the difficulty of prosecuting cases. They point out that gun prosecutions have actually declined under Obama and argue that he's trying to abuse the current laws to go after law-abiding citizens.

Fewer gun cases than crimes

What is not disputed is that federal prosecutors bring far fewer cases against gun crimes than the amount of crime suggests they could.

Jennifer Baker of the NRA cited her group's calculation that federal gun prosecutions have declined 40% under Obama's administration, after peaking in 2004.

Taya Kyle, the widow of Navy SEAL Chris Kyle, who was murdered at a shooting range, seemed to refer to the NRA's statistic Thursday night in challenging Obama on his efforts to impose more gun regulations.

"Last I heard, the federal prosecution of gun crimes was like 40%. And what I mean by that is that there are people lying on these forms already, and we're not prosecuting them. So there's an issue there, right?" Kyle asked Obama.

Obama did not answer that specific point of her question, making a case that a decline in violent crime rates does not mean guns can't be made safer. He also repeatedly said that not solving all problems is not a reason not to try to solve any.

But gun-control groups argue that even the 2004 mark wasn't much of a peak. A 2003 study by Americans for Gun Safety, which is now a part of Third Way, found that over three years, roughly 2% of federal gun crimes were prosecuted.

Further, they found that 85% of prosecutions were under two laws -- possession of a firearm by a felon and possession of a firearm while committing another federal crime -- and that President George W. Bush focused on those two statutes in increasing gun prosecutions. That left 20 federal gun laws virtually unused, per their analysis.

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Though the study was conducted in 2003, Third Way senior policy counsel Sarah Trumble said she doubts a study conducted today would find much difference.

The problem is several-fold, the gun-control groups say, and Obama's executive actions are geared toward trying to close the enforcement gap.

One is simply a resource problem: The Bureau of Alcohol, Tobacco, Firearms and Explosives, or ATF, which investigates licensed gun dealers, and the National Instant Criminal Background Check System are woefully understaffed and replete with red tape, gun control supporters say.

The groups also say the federal laws themselves have such high standards to meet in court that it's a disincentive for resource-strapped federal prosecutor offices to bring cases, as they don't want to waste their time on cases they are not likely to win.

"It is true that gun laws are vastly under-enforced, but the reason that they're under-enforced is not because the administration or law enforcement has failed: It's because they're written in a way that makes them impossible to enforce -- intentionally," Trumble said. "They're too vague to prosecute, the standards are too high to meet, the penalties are too low to be a deterrent and there's too little evidence to prosecute."

The Gun Control Act requires those "engaged in the business" of selling firearms to obtain a license from ATF, and licensed dealers are required to run background checks and follow federal laws on dealing weapons. But what constitutes "engaged in the business" has been unclear, and prosecutors say it can be tough to prove unlicensed individuals who sell multiple weapons online and at gun shows have broken the law.

That is the focus of one of Obama's actions, under which the ATF put out a clarification of what it believes that statute means, which could help prosecutors and gun sellers better understand the law.

Prosecutors take "engaged in the business" cases that are referred to them at a far lower rate than other kinds of crime, says Everytown for Gun Safety, a group formed after the massacre in Newtown, Connecticut, in 2013. According to their analysis, 54% of those cases are prosecuted, as opposed to 77% of drug trafficking crimes.

A tough call for prosecutors

It's a tough call for prosecutors to make, said Jenny Durkan, a partner at Quinn Emanuel who was the U.S. attorney in Western Washington state for five years under Obama.

"You have a pretty finite and limited budget and resources to address pretty widespread problems in a district," Durkan said. "The law on (engagaing in the business) is a really difficult standard to meet. To prove that someone is in the business of selling guns is very, very difficult."

Durkan did successfully prosecute illegal gun sellers in her district, but she said her one big case of note was strengthened by evidence of tax evasion as well.

She said the clarification put out by the Obama administration Tuesday will be helpful but not all-powerful. She and Ted Alcorn of Everytown said better enforcement could help alongside sorely needed cultural change.

"So much about law is about setting cultural norms," Alcorn said. "Just like the reasons you stop at red lights and don't speed isn't because there's a traffic cop behind every corner."

Instead, he said, it's "the sense that a law is legitimate, that it enforces public safety that we all share and all appreciate, and a sense of ownership and mutual responsibility are sort of ultimately self-fulfilling."

Obama's actions also aim to get at the resource problem, though he will need Congress to back him up. Obama is calling for 200 more ATF agents and 230 more National Instant Criminal Background Check System examiners, but the money will have to be allocated by lawmakers.

Beefing up the agency will be essential, former ATF Special Agent in Charge Joseph Vince said.

Both underfunding and vague laws "are strategies that the gun lobbyists use to keep gun laws from being enforced," Vince said. "As ATF is not able to go out and look at gun dealers, then people start to push the envelope more and more."

According to ATF, the agency had 780 investigators and 2,490 special agents in 2014. ATF declined to comment on the adequacy of its resources.

"If you look at a medium-sized police department in the United States, it has more sworn officers than ATF has in the whole country, and that's for 50 states and territories," Vince said.

Vince also complained of burdensome restrictions on ATF -- including only being able to inspect gun sellers once a year -- that other agencies with similar mandates don't face.

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But gun-rights groups say any effort to use today's lack of enforcement to push for new gun measures is a ruse.

"There was a peak of federal gun prosecutions under Bush in 2004, the laws have not changed since that point, and under the leadership of President Obama, there's been a 40% decline in federal gun prosecutions," Baker said. "It begs the question, why aren't you enforcing the laws on the books?"

She said that arguments about weak laws are misplaced.

"This administration is vehemently anti-gun, and what they did this week ... is they merely re-stated the current law. But the abuse is going to come in the implementation, and what they are trying to do is chill lawful behavior by law-abiding individuals through intimidation," Baker said.

John Malcolm, a senior fellow at the Heritage Foundation, said as a former prosecutor, he is not persuaded that current gun laws are too difficult to use.

"The laws do not strike me as being so loose that they are being incapable of successful enforcement actions, and in fact people are prosecuted for being unlicensed firearms dealers," Malcolm said. "My guess is, if they devoted more resources to prosecute these laws, they could."

He also said that any restrictions on ATF may be warranted.

"ATF has, and deservedly so, has taken it on the chin for operations like Fast and Furious, and it could be they have approval processes that are overly draconian," he said, referring to the sting operation gone wrong in which the agency tried to supply guns to cartels to catch criminals but ended up losing track of many of the weapons.

Malcolm also cast doubt on whether the President's proposals would do anything to address the issues the other side raises, given that an ATF clarification does not carry the weight of a regulation or law. It will be up to judges and prosecutors how the ATF's guidance matters to prosecutions.

It's unclear to Obama's supporters whether the guidance the White House disseminated will be followed up by an agency rule, but they are hopeful the emphasis from the Obama administration will empower prosecutors to go after the big cases more often.

"The teeth are what we're going to see in coming months and years as these cases are prosecuted," said Robyn Thomas, executive director of the Law Center to Prevent Gun Violence. "The fact that this is now clarification that U.S. attorneys can use when prosecuting, and the fact that they are being pushed to do these prosecutions and look into these cases more closely, the teeth aren't in the regulation, they're in how they're applied."